Surface chemistry_XII Flashcards
Adsorption
Surface phenomenon.
Its the increase in concentration (aggregation) of any molecule at the surface rather than at bulk.
May occur above a ‘solid’ or ‘liquid’ surface. **(not gaseous surface =common sense hai gas pe koi particle kese ruk payega).
Adsorbent
Solid or liquid surface ON which molecular species are adsorbed.
Adsorbate
Molecular species which IS adsorbed on the surface.
Absorption is a _____ phenomenon whereas adsorption is ____ phenomenon.
A’b’sorption = ‘b’ulk phenomenon Adsorption = surface phenomenon
CaCl2 ______water vapours ; silica gel _____ water vapours.
Absorbs/adsorbs
CaCl2 absorbs water vapours ; silica gel adsorbs water vapours.
Desorption
When molecular species are removed from the surface.
Occlusion
Adsorption of gas on solid surface.
Adsorption is _______[exo/endo thermic] process.
Exothermic (heat is released).
Δ H -ve
Δ S -ve (entropy of gas molecules decreases)
For the process to be spontaneous, magnitude of;
Δ H
Δ G
Δ H > T ΔS i.e ΔG<0 (-ve)
On increasing temperature, magnitude of T ΔS _____ & ΔG _____.
Magnitude of T ΔS increases whereas |ΔG| decreases
Select correct statements regarding Physical adsorption (physisorption):
a) not specific.
b) reversible.
c) results in multilayer adsorption
d) not.
c) all of these.
All of these.
It decreases with increase in temperature.
Physisorption ______ with increase in temperature.
Decreases.
Chemisorption _______ with increase in temperature.
Increases with increase in surface area.
First increase , attains maximum & then decreases.
In Freundlich isotherm, value of 1/n & n ranges from?
1/n = 0.1 - 0.5
=> n = 2 - 10
According to ______theory all adsorption sites are equivalent.
Langmuir isotherm.
Greater the surafce area _____ is the rate if adsorption.
Greater.
Porous surfaces will show more rate of adsorption.
KClO3 ———>KCl +3/2 O2
Write the catalyst involved?
MnO2
Temp.= 400-600K
What’s promotor?
Increases activity of catalyst.
Eg,s MO & K2O are used in Haber’s process as promoter.
What’s poison?
Decreases activity of catalyst.
Egs., As, Co, Quinoline
SO2 + ½ O2 ———>SO3
Is an example of ?
Homogeneous catalysis, if catalyst used is NO (g)
Heterogeneous catalysis, if catalyst used in V2O5. [Contact process]
SO2 + ½ O2 ———>SO3
Is homogeneous catalysis if catalyst is
NO (g)
*reaction/process is called ‘lead chamber process’.
SO2 + ½ O2 ———>SO3
Is heterogeneous catalysis if catalyst used is
V2O5
*reaction/process is called CONTACT PROCESS .
This is one of 3 MOST IMPORTANT RXNS.
CH3COOC2H5 + H2O ———>CH3COOH + C2H5OH
Ester. Water. C.acid. Alcohol
whats the catalyst used for this homogeneous catalysis rxn.
H+ (aq.)
C12H22O11(sucrose/sugar) + H2O ———> C6H12O6 (Glucose) + C6H12O6(fructose)
Catalyst used??
H+ (aq.)
Examples of heterogeneous catalysis?
the 3 most important rxns.
Contact process: SO2 + ½ O2 ———>SO3 (V2O5 as catalyst)
Haber’s process: N2 + 3H2 ———>2NH3 (Fe as catalyst; Mo as promoter)
Ostwald’s process: NH3 + O2 ———>NO + H2O (Pt as catalyst)
Na2SO3 ———> Na2SO4
In presence of Na2ArO3 (sod. Arsenate) & O2
Is an example of induced catalysis
Example of auto-catalysis?
MnO4 + C2O4 + H+ ———> Mn+2 + CO2 + H2O
Here, Mn+2 produced is used as catalyst for the rxn.
According to modern adsorption, what’s the mechanism of catalysis?
Diffusion>adsorption>reaction>desorption>diffusion.
Zeolites/selective shape catalyst?
Hydrated sodium aluminium silicates. (3D str.)
ZSM-5 a zeolite, acts as catalyst for
Alcohols(R-OH) into gasoline(R-H) i.e dehydrates
1) CO + H2 ———>CH4 + H2O
2) CO + H2 ———>CH3OH
3) CO + H2 ———>HCHO
Write catalysts for each of these?
1) CO + H2 ———>CH4 + H2O ; Ni
2) CO + H2 ———>CH3OH ;CuO/ZnO-CH2O3
3) CO + H2 ———>HCHO ; Heat only
Sugar(C6H22O11) +H2O ———> Glucose + fructose
Name the enzyme catalysis?
Invertase.
C6H12O6 ———>C2H5OH + CO2
Zymase.
(C6H12O6)n———> C6H22O11 (maltose)
Diastase.
C12H22O11 + h2o ———> C6H12O6 (glucose)
Maltose.
NH2CONH2 (Urea) + H2O ———>NH3 + CO2
Urease.
Proteins ———>peptides ———>aminoacids
Proteins ———> peptides. ; Pepsin
Peptides ———> amino acids. ;Trypsin
Triglycerides ———>glycerol + fatty acids
Lipase
Activators
Metal ions like Na+ , Mn+2, CO+2
Co-enzymes are ?
Substances which increases activity of enzymes.
Inhibitors destroy the catalytic activity of enzymes.
Poisons are substances which slows down activity of enzymes.
- both correct
-both incorrect
- 1st correct
- 2nd correct
Both are correct.
Mention particle size in each of these:
A) true solution
B) colloidal solution
C) suspension
A) true solution = less than 10 A°
B) colloidal solution = 10-10^4 A°
C) suspension = greater 10^4 A°
Adsorption isostere are
Plot at constant x/m b/w pressure and temperature.
For adsorption generally ΔH, ΔG, ΔS are: \+,-,+ \+,-,- -,+,- -,-,-,
ΔH -ve
ΔG -ve
ΔS -ve
In freundlich isotherm, slope of plot of log x/m vs log p gives
Value of 1/n
According to langmuir isotherm, amount of gas adsorbed at very low pressure is
Directly proportional to pressure.
According to langmuir isotherm, amount of gas adsorbed at high pressure is
Independent of pressure as at high pressure x/m is constant.
For langmuir isotherm; Slope of straight line of plot of P/(x/m) vs P graph gives/is
b/a
Where b and a are langmuir parameters .
Also, the intercept if this graph = 1/a
Ultra filter paper used in ultrafiltration is prepared by
Soaking a filter paper in a colloidal soln. (4% soln. Of nitro cellulose in a mixture of alcohol and ether) hardening by formaldehyde and then dried.
Tyndall effect is not shown by true solutions.
T/F
True
Tyndall effect is due to
Scattering of light by colloidal particles (dispersion phase)
FeCl3 added in excess hot water forms a positively charged sol of hydrated ferric oxide.
(T/F)
True.
And a negatively charged sol when FeCl3 is added in NaOH due to adsorption of OH- ions
Electrokinetic potential or zeta potential is?
Difference in potential b/w electrical double layer of opposite charge (called Helmontz electrical double layer) is c/d zeta potential
Coagulating power is inversely proportional to coagulation value.
(T/F)
True
Colloidal antimony is used in curing
Kalazaar
_______ sol is used as an eye lotion.
Argyrol in silver sol
Colloidal gold is used for
Intramuscular injection
_______ is an emulsion used for stomach disorder.
Milk of magnesia.
4 methods to coagulate lyophobic colloids?
Electrophoresis
By mixing 2 opposite charged sols
By boiling
By addition of electrolytes
